Detachable plug



Half

F. E. TIFFANY '-DETACH ABLE PLUG Fil ed Jan. 2, 1

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1 a m a March 19 1946.

YINI/ENTOR v FRANK E.T1FFANY Patented Mar. 19, 1946 DETACHABLE PLUGFrank E. Tiffany, Claremont, Callfl, assignor, by mesne assignments, toLockheed Aircraft Corporatioma corporation oiCaliiornia I ApplicationJanuary 2, 1943, Serial 'No. 471,201 4 Claims. (01. 173-361) Thisinvention relates to, a new and improved device for connecting leads ofelectrical devices such as, for instance, as are used in operatingportable electrical devices, and has special reference to detachable twoor more terminals as in so-called high'cycle or multi-phase connectors,which may also carry a ground connection.

In the use of commercially available connector plugs for port-ableelectrical tools and equipment, considerable trouble has beenexperiencedboth due to the extended contacts and to ignorant or careless insertionand removal of such plugs from their complementary extension couplings,convenience outlets, receptacles, etc. The extending prongs or contactblades become damaged from lying around on the floor or being droppedthereon, and inexperienced employees may further damage the plugs byattempting to straighten the blades, force the plugs into thereceptacles in improper alignment, or to pry the blades out of theirreceptacles when disconnecting the same.

It is an object of this invention to provide novel means for protectingthe binding posts of such plugs when the device is not in use.

Another object of the invention' is to provide novel means of recessinga plug into a socket to prevent the harmful and hazardous insertion of ascrewdriver, or similar object, between the plug and socket to pry thetwo apart. r

A further object of the invention is to provide a simple effectiveelectrical plug having a contact blade cover which retracts when theplug is inserted into a socket, and which automatically advances overthe cont-act blades of the plug when the plug is removed from thesocket.

Other and further important objects of this invention will be apparentfrom the disclosures in the specification and the accompanying drawing.

This invention in its preferred form isillustrated in the drawing andhereinafter more fully described.

In the drawing:

Figure I is a side elevation showing one embodiment of my inventionas'applied to a heavyduty or multi-phase connector.

Figure II is a sectional elevation thereof with the contact blade coverin its extended position wherein it envelops'and protects the blades.

Figure III is a sectional elevation of a plug and socket with thecontact blade cover in its retracted position.

Figure IV is a bottom Figure I.

As shown in the drawing:

I have chosen to illustrate an embodiment of my invention designed tointerchange with comview of the plug of mercially available plugs suchas are in common use for heavy duty services in industrialestabllshments where portable electric tools are in electricalconnectors having 5 use. The particular type and arrangement ofterminals or contact blades illustrated correspond to a so-called"twist-lock is pushed straight in and then slightly turned to lock it inplace.

The present invention relates particularly to devices adapted for makingdetachable electrical connections, such, for example, as are used forconnecting electric motors and other portable electrical devices tosources of current supply, such as wall or floor or other convenienceoutlets in garages and factories, and includes a plug cap generallydesignated Ill, a socket which may be in the form of a conventional wallor portable receptacle or mating plug, shown without details andgenerally designated as l I, and an insulating contact blade cover l2.The plug cap l0 consists of a suitable shell or casing l3 having a cordaperture in its nearly closed top. An annular insulating and supportingmember I5, is arranged in the upper portion of the shell I3 and has aninwardly extending portion l6 which supports legs I! of inwardly andthen outwardly extending complementary members l8 which are adapted tobe clamped together to hold the lead in cord in place. A, support member2| having its top side against the lower face of member l5 is removablymounted inside of the shell l3 and supports a series of contact blades23, arranged to form a circular pattern having unequal radii from thecenter of blade cover l2. As shown, three of these live terminals may beused and a similar fourth or ground terminal blade 24 may be oiisetrelative to the others the corresponding receptacle, mating coupling, orconvenience outlet. For readyidentiflcation of the ofiset terminal, itmay be made slightly larger and/or longer than the a portion 25protrudes beyond the lower surface of blade cover I2. Contact blades 23and 24 each have a lateral portion 26 extending sideways therefrom in aclockwise direction.

At the uppermost end of contact blades 23 and 5 24, I providefourbinding posts 21, which may be of the conventional type to formattachments for electrical wire lead-ins.

A peripheral shoulder 29 is formed on the lower portion of supportmember 2| and adjacent the 0 shell l3. A similar shoulder 30 is providedon the upper portion of blade cover l2 adjacent shell i3, and the twoshoulders leave a recess to accommodate a compression spring 3|. Screws32 attached to blade cover l2 are adapted to travel upward and downwardwith the blade .cover l2 in slots 33 out vertically in the lower portionof shell l3. The screws 32 are engageable with the ends of the slots tolimit the travel of the cover l2.

On the upper face of socket II, I provide a raised portion 34 having aninside radius slightly plug where the plug to properly locate the liveterminals relative tov live terminals 23 so that larger than that of theplug I and extending above the lower surface of plug cap II) and bladecover I2 to provide a recess into which plug cap I0 seats when theconnection is completed.

Assuming that the various contacts of the devices each have a lead wireconnected with them, when it is desired to connect the plug II! with thesocket II, contact blade 24 is inserted into its slot'in the socket IIto obtain alignment. By applying pressure to the top of shell I3, theblade cover is depressed, compressing spring 3|. By turning the plug capIII clockwise, the lateral portions 26 or the blades 23 and 24 arecaused to look into suitable contacts in the socket II. Thus it can be.seen that when plug cap III is seated, it is recessed into socket IIpreventing the possible harmful and hazardous insertion of a screwdriveror similar article between cap I0 and socket I I to efiect theirseparation.

In removing the plug I0 from the socket I I, the plug I0 is slightlyturned counterclockwise and lifted upward, whereupon the blade cover I2is extended over the contact blades 23' and 24 by the compression spring3|, preventing any injury to the contact blades 23 and 24 during thetime the plug is disconnected from its socket.

It will thus be seen that 1 have invented an improved safety plugwherein the contact blades or terminals of the detached plug are againstaccidental injury while lying around under foot, and in which ignorantor careless operators cannot bend or distort the terminals in attemptsat improper assembly and cannot injure themselves by trying to pry theplug out of the receptacles by inserting a tool between the plug and thereceptacle.

Having thus described my invention and the present preferred embodimentthereof, I desire to emphasize the fact that many modifications may beresorted to in a manner limited only by a just interpretation of thefollowing claims.

I claim as my invention:

1. An electrical multi-circuit connecting plug for removable engagementwith convenience outlets or the like, comprising an enveloping shellhaving an end wall with an opening therein to receive a multiple leadcable, an insulated mounting block positioned within said shell adjacentsaid end wall thereof, a plurality of blade contacts carried by saidmounting block and mounted in general parallel relation with the axis ofsaid shell, said blade contacts extending out of and beyond the otherend of said shell to, engage with said outlet,- one of said bladecontacts being varied in length relative to the others to identify thesame, and in its relative position with respect to the others to orientthe plug relative to its outlet, a second insulating block havingapertures therethrough through which said blade contacts extend, saidsecond block being so constructed and arranged as to slide in andpartially out of said shell whereby in its extended or outer position itsubstantially embraces and covers the projecting portions of said bladecontacts, and a single spring arranged under compression between saidblocks for yieldingly projecting said second block to its outer positionupon disengagement of the plug from an outlet, said spring surroundingsaid plurality of blade contacts.

2. An electrical plug for removable engagement with an outlet, or thelike, comprising a shell having an end wall provided with an opening forprotected guard block slidable in the receiving a multiple lead cable, ablock secured in the shell adjacent said end wall and having spacedapertures, a plurality of spaced contact blades attached to said blockand extending through said apertures and continuing outwardly throughthe shell to project beyond the other end thereof for engagement with anoutlet, the engagement of the blades in said block sustaining the bladesagainst lateral displacement, a second block slidable in the shell andhaving spaced apertures slidably receiving the blades to guard theblades and to sustain the blades against lateral displacement, saidsecond block being movable between an extended position where itsubstantially covers the' projecting portions of the blades and aretracted position where it is substantially entirely within the shell,and means for yieldingly urging said second block to its extendedposition comprising a helical spring in surrounding relation to theplurality of blades and engaged under compression between the firstnamed block and said second block. p

3. An electrical plug for removable engagement with an outlet, or thelike, comprising a shell having an opening in one end for receiving amultiple lead cable, a plurality of contact blades secured in the shellfor connection with the cable leads and extending longitudinally throughthe shell to project beyond its other end for engagement with an outlet,one blade projecting beyond the shell a greater distance than the otherblades, a

shell and having apertures slidably receiving the blades, the blockbeing movable between an extended position where it projects from saidother end of the shell to form a guard for the projecting portions ofthe blades and a retracted position within the shell, said one bladebeing the only blade that projects from the block when the block is inits extended position, and a single helical spring in the shell insurrounding relation to the plurality of blades and acting outwardlyagainst the block for yieldingly urging the block to its extendedposition.

4. An electrical plug for removable engagement with an outlet, or thelike, comprising a shell having an opening in one end for receiving amultiple lead cable, a block secured in the shell adjacent said end andhaving spaced apertures, contact blades attached to said block andextending through said apertures and continuing outwardly through theshell to project beyond the other end thereof for engagement with anoutlet, the engagement of the blades in said block sustaining the bladesagainst lateral displacement, 9. second block slidable in the shell andhaving spaced apertures slidably receiving the blades to guard theblades and to sustain the blades against lateral displacement, saidsecond block being movable between an extended position where itsubstantially covers the projecting portions of the blades and aretracted position where it is substantially entirely within the shell,

and has its inner end contacting or adjacent the opposing end of thefirst named block, said ends of the blocks being formed and related toleave an annular space in the shell adjacent the side wall thereof whensaid second block is in its retracted position, and a spring in saidspace in spaced surrounding relation to the plurality 01 contact bladesand under compression between the blocks for yieldingly urging saidsecond block to its extended position.

